Video telephony refers to "picture telephones" in which bi-directional video and audio links are established between calling and called parties. It also includes teleconferencing, in which digital images, such as text and graphics, may be displayed adjacent video images of the conferees or subscribers. In either system, it is desirable to create an illusion of eye contact between or among the subscribers. That is, it is desirable that when, for example, a called party views the image of the calling party, the called party sees the image of the calling party such that the eyes of the calling party are directed outwardly from the display screen upon which the calling party's image is displayed and appear to look at the called party.
The patent of Gitlin et al., U.S. Pat. No. 5,159,445, issued Oct. 27, 1992, is an example of apparatus for creating the eye contact illusion. The image display is an image projection screen interposed directly between the subscriber and the camera transmitting the image of the subscriber. The screen rapidly switches between a projection mode during which it reflects and projects the image seen by the subscriber, and a transmission mode, during which the screen is transparent, and the image of the subscriber is recorded by the television camera. The subscriber naturally looks at the screen, and thus directly into the camera, when viewing the display. Consequently, the transmitted image of the subscriber shows the subscriber's eyes looking directly outwardly.
The provision of a screen that is alternately reflective and transparent significantly complicates the video telephone system in which it is used and makes it more expensive. It would be desirable to provide a system that gives the illusion of eye contact without significantly increasing the cost or complexity of the system.
The paper, "New Eye-Contact Technique for Videophones," H. Arai et al., SID 92 Digest, Society for Information Display, Playa del Ray, Calif., U.S.A, 1992, pp. 149-152, is an example of "passive" systems in which a beam splitter is located between the subscriber and the video display. The beam splitter, e.g., a blazed grating, directs the viewer's image at a video camera as the viewer looks directly at the display through the beam splitter. This has several disadvantages, among which is the fact that the beam splitter screen cannot be used as a projection screen. Projection screens are advantageous because they can be used to project a larger image than that produced, for example, by a cathode ray display. Making and using appropriate beam splitters such as blazed gratings also may present problems. New methods of making microlens arrays allow projection screens to project images with enhanced optical efficiency, and it would be desirable to take advantage of such technology.